1. Field of the Invention
This invention is related to the field of integrated circuits and, more particularly, to controlling supply voltage to an integrated circuit.
2. Description of the Related Art
As the number of transistors included on a single integrated circuit “chip” has increased and as the operating frequency of the integrated circuits has increased, the management of power consumed by an integrated circuit has continued to increase in importance. If power consumption is not managed, meeting the thermal requirements of the integrated circuit (e.g. providing components required to adequately cool the integrated circuit during operation to remain within thermal limits of the integrated circuit) may be overly costly or even infeasible. Additionally, in some applications such as battery powered devices, managing power consumption in an integrated circuit may be key to providing acceptable battery life.
Power consumption in an integrated circuit is related to the supply voltage provided to the integrated circuit. For example, many digital logic circuits represent a binary one and a binary zero as the supply voltage and ground voltage, respectively (or vice versa). As digital logic evaluates during operation, signals frequently transition fully from one voltage to the other. Thus, the power consumed in an integrated circuit is dependent on the magnitude of the supply voltage relative to the ground voltage. Reducing the supply voltage generally leads to reduced power consumption, but also impacts the speed at which digital circuits operate and thus may cause incorrect operation at a given operating frequency (that is, the frequency at which digital logic in the integrated circuit is clocked).
Additionally, as transistor geometries have continued to decrease in size, leakage currents that occur when a transistor is not actively conducting current have become a larger component of the power consumed in the integrated circuit. The amount of leakage current experienced in a given transistor generally increases exponentially as the supply voltage increases.
Thus, power consumption in an integrated circuit may be managed by lowering the supply voltage to the integrated circuit, but incorrect operation may also result if the supply voltage is reduced too far. The supply voltage magnitude at which incorrect operation occurs for a given operating frequency varies on part-by-part basis for a given integrated circuit design. For example, variations in the integrated circuit manufacturing process used to manufacture the integrated circuit and the operating temperature of the integrated circuit may both impact the supply voltage magnitude at which incorrect operation occurs. Accordingly, attempts to manage power consumption via the supply voltage have been limited to supply voltage magnitudes that ensure correct operation at the given frequency across all acceptable variations in the manufacturing process and all permissible operating temperatures. Typically, the supply voltage for a given frequency is statically specified in the integrated circuit's specification.